Piston



J. W. BROWN May 15, 1951 PISTON Filed Sept. 7, 1948 Fla? Patented May15, 1951 YUNVFED S TATIES Il'ieA'lErPJ T O FFIC E PISTON JamesW.'-.Br0wn, Oakland, Calif.

'Application September 7, 1948, Serial No.48;003

7 Claims. .1

Thisinven'tion relates itofa f piston '.'cons'tructi'on of the type`,used fin reciprocating .engines '.of the internal 'combustion class.It is #conventional practice 'to allow for lpiston expansion fin suchrengines'fby g'rinding 'the pistons ito :substantially :smaller sizethan theibor'efof-thefcylinders willich tney fare 'to dit, and then 5to'employ 1 compression frings to maintain .a substantially lgas:tightseal between feachpiston and' itsflcylinder.

Tin v"the ease 4v'of what lare called fcameground Ypiston-s, the pistoniis fovaI Tin shape having its major dimensionsalcngfalinelatfarightiangleito A"tlfiefcent'er of ktl'ieaiiis fo'f thewrlist pin .".so `that 'Pits 't Within 'the cylinder iis l'closestfoppo'site fthe rends ff `said "lineand ithe tendencyfof the lfpistcn tomeek on theaiisfo'f .the'iwrisltpin `and 'cock ithe :sharp *edges dffthe compression rings into fenlgagement with 'the cylinder walls `lisminimized. `However, it isnecess'ary even infsuchconstructions itoyallow fa minimum oi 20005 linch fclearance "betweenthe :cylinder and thepiston'atftheplaces 'just described and lt'o allow forexpans'ion 'ofthepiston with respect lto :lits cylinder by :allowing greater Eclearancebetween :these iplace's, :so 'ithat :as the ipiston fexpands 'itmay `bedeformed from its foriginal :oval .fsnape Ito ra tmoreinearly .freundEsh'ape.

In the :case of vround-grcun pistons which are `truly `round. Ain shape,much larger -minimum clearances between the pistons and cylinders must.-b'e fallowed fatwall :points in :order fto :permit expansion of reachipistonwrelatve ito its-cylinder, and thetendency of therpistontto-rockion the :axis -of the fwristpin Iandncock -the fsharpt-edges .ofrthe Ycompression vrings finto v.engagement with .the icylinder 'Wallsis `'even #greater than iin the case of icamgroundpistons.

In .either case, `theamount of .such Acocking is suicient to produce,greater v.wear of the .cylinader rwalls in the areas generally opposite4the yends of a -line drawn `at `a right/.angle gto .the .center .of.theax'is Aof .the wristip-ingso that each cylinder Wears -unequall-yand =compression is gradually decreased,

It is 'thepr'incipal .objecto'f the present'inven- 'Jtion tomakeposs'ible a substantiallyv closer "fitting Yf the piston structuresWithin the cylinders of internal ccmbustion engines, withoutriskof'seiz- "ure occurring 'by 'reason o'f 'expansion 'of the ,piston'srelative"totheircylinders 'By thusfdecreasing the clearance betweenpiston 'and cylinder, "the Acooking tendency referred *to labove `isV'decreased to thepeintof substantial elimination, and 'the v'resultingwear "of "the Jcylinder walls fin `the 'areas mentioned '-is notsubstantially greater l2 than in` any other 'area adjacent the piston,-even Where oil rings, or even lightcom-pression rings are Iusedalthoughfcompression rings of .the Ausual type are unnecessary `withtheipiston` of the present invention.

A further and important .objectof `.the-invention kis to make possiblefa .closer nfit `of cylinder and piston in the area of the piston lying.generally above Ythe axis of ytl'ie-wrist..pin,ithereby still furtherdecreasing .the .co.cking tendenc7 Y.previously mentioned.

.LA .still kfurther and Very .important .object `of the invention .is to,provide a piston construction which will have substantially as close 'a't Within the -cylinder lwhen cold as it lhas at operating temperatures,therebygleatly reducing the cylinder .xvearincidentfto cold starting;which Wear is very great in .conventional lconstructions 'in which`clearances `of the order previously men- Aaccessory oil ring isemployed.

In the pref-erred'embodiments offthevinvention the 'piston structure.consists-essentially of three lprincipal parts.

The fouter body, or sleeve lil, preferably of Vcast iron,.is formed withacircurn- .ferential internal vgroove -|YI. .Inside vthe -upperportionof sleeve l) there -is .a ^thineilexible steel ring .or band I2brazed or other-wise ,secured arc-und its upper edge to theinnermarginofthe sleeve ld, Vas. at i3, witnits .lower edgeat about .the center ofgroove Internally of these there'is the innerpiston ,bodyiandhead Mwhich Ain .the embodiment illustrated 4is 'equal in vertical dimensiontothe outer Sleeve'ili. The inner bcdy /Z is an .aluminum alloy pressuredie casting which is preferably 'cast into the sleeve iii 'and ring l2to complete the piston. Tlie'aluminurn alloy is preferably `cast intothesleeve and rins in"moltenstate and inthe process of casting some of themetal is for'cedinto'groove H andinto'intimate contact with bothside'softheY lower 'edge or the flexible -steelfring -I72,asat l5; andas it cools and shrinks it will vform 'an aire'tight 'seal with thering. However, the inner body may be machined to the same dimensions itwould have if so cast, and an air-tight seal with the ring I2 effectedby any desired means. The annular lug I6 produced by now of the metalinto groove II effectively locks the cast iron sleeve I against verticalmovement with respect to the aluminum piston body I 4. In theconstruction of Figures l and 2, as well as in the modifications ofFigures 3 and 4, to be referred to, the aluminum'alloy cast in moltenstate will contact the inner surfaces of sleeve I0 and ring I2, asillustrated by Figure 1. As the casting cools and contracts, it willshrink away from sleeve I0 as illustrated by Figure 2 and the elementsof the assembly will assume substantially the relation there shown, thelower end of the flexible steel ring I2 being drawn away from sleeve Illwith lug I while preserving an air-tight seal at the joint.

same manner as in the first construction described.

The modification of Figure 4 differs from that of Figures l and 2 onlyin the provision of a ring groove Il in the outer sleeve l0 d-esigned toreceive an oil ring I8. In this construction the cast iron sleeve I0 isthickened at the groove location to provide the required ring seat, asshown,

forming an annular protuberance I9 on the inner surface of the sleeve.This serves as an addition al lock between the aluminum inner piston Itand the sleeve I B. After the aluminum piston is cast, as beforedescribed, circumferential oil drain apertures 20 preferably areprovided as by drilling through the bottom of groove Il and the skirt ofpiston I4 as shown.

As well known to the art, the head of a piston is subjected to thehighest heat and will expand against the cylinder wall under conditionsproducing high heat and contract away under conditions of low heat andis, therefore, the most troublesome part of a piston. With the piston ofthe present invention, the head is poured into the cast iron sleeve in amolten state. As it cools it shrinks away from the sleeve which is incontact with the cylinder wall. Under operating conditions the aluminumpiston and head will never become as hot as when it was formed and socan never expand to a degree where it would put pressure on the castiron sleeve and force it against the cylinder wall. The cast outersleeve will, therefore, tend to run at an equal temperature to the castiron cylinder wall and if any eX- pansion or contraction takes place inthe cylinder wall, it will be practically constant with that of the castiron piston sleeve. Hence, when the cast sleeve of the piston hereindisclosed is either lapped into a cylinder or ground to equivalentdimensions there will be a constant fit under operating conditionsbetween the cylinder and piston. Furthermore, use of aluminum for theinner body and head of the piston will result in a considerablereduction in weight with a consequent gain in engine efficiency.

Utilizing pistons embodying the present invention it has been foundpossible to employ round ground piston constructions in which, in a onecylinder, one and three quarter inch bore, air--r cooled, four cycleengine, a clearance of only .0002 of an inch was maintained between thepiston sleeves and the cylinder walls, and completely successfulioperation was demonstrated by an extended test.

It will be evident from the above disclosure that a simplified andhighly efficient piston construction has been provided by this inventionand that further modifications of the structures disclosed could be madewithout departure from the scope of the invention as defined in theclaims.

What is claimed is:

1. In a piston for reciprocating engines, an outer cast iron sleeveformed with a circumferential groove in its inner surface, an integralaluminum body and head co-extensive with said sleeve and fitted withinthe sleeve with an integral circumferential lug projecting into saidgroove, and a continuous flexible steel band positioned between thesleeve and body adjacent the upper ends thereof and having its oppositeedges sealed to the sleeve and body respectively.

2. In a piston for reciprocating engines, an outer cast iron sleeve, aninner aluminum head and bodyV co-eXtensive with said sleeve fittedwithin the sleeve, interlocking elements between the sleeve and body forpreventing relative movement longitudinally, and a continuous exiblesteel band positioned between the sleeve and body and having itsopposite edges sealed to the sleeve and body respectively.

3. In a piston for reciprocating engines, an outer cast iron sleeve, aninner aluminum head and body fitted within said sleeve, interlockingelements between the sleeve and body for preventing relative movementlongitudinally, and a. continuous flexible steel band positioned betweenthe sleeve and body and having its opposite edges sealed to the sleeveand body respectively.

4. In a piston for reciprocating engines, an outer cylinder engagingsleeve, an inner body forming the piston head fitted within said sleeveand formed of an alloy having a higher coeflicient of expansion than thesleeve, means on the sleeve and'body for preventing relativelongitudinal movement, and a continuous flexible metal band having itsopposite edges in sealed union with the sleeve and inner bodyrespectively.

5. In a piston for reciprocating engines, an outer cylinder engagingsleeve, an inner body of aluminum alloy, forming the piston head, castwithin said sleeve, interlocking means between the sleeve and body forpreventing relative longitudinal movement, and a continuous flexiblemetal seal uniting the sleeve and body.

6. In a piston for reciprocating engines, an outer cast iron sleeveformed with a circumferential groove in its inner surface, a secondcircumferential groove formed on the outer surface of the sleeve belowthe location of the internal groove and provided with oil drainageapertures in its base, an inner aluminum head and body fitted withinsaid sleeve and formed with a projecting portion engaged in saidinternal groove, a flexible metal band positioned between the sleeve andbody adjacent the upper ends thereof and havingfits upper edge sealed tothe upper edge of the sleeve and its lower edge sealed to the body atthe portion thereof project- .ing into the internal groove, and an oilring seated in the external circumferential groove.

'7. In a piston for reciprocating engines, an

5 6 outer cylinder-engaging sleeve, an inner body REFERENCES CITEDforming the piston head tted within said sleeve The following referencesare of record in the and formed of an alloy having a higher coefme ofthis patent: cient of expansion than the sleeve, means on the sleeve andbody for preventing relative longi- UNITED STATES PATENTS tudinalmovement, and a relatively thin elon- Number Name Date gate metal bandhaving its opposite edges in 1,733,422 Mertz Oct. 29, 1929 sealed unionwith the sleeve and inner body 1,916,978 Harper, Jr July 4, 1933respectively. 2,390,586 Hastings Dec. 11, 1945 JAMES W. BROWN. i0FOREIGN PATENTS Number Country Date 338,707 Great Britain Nov. 27, 1930

